This report describes the case of a 20-year-old man who sustained a gunshot wound to the forehead, resulting in traumatic brain injury and C2 ventilator-dependent quadriplegia. Issues of personal control and autonomy typified his psychological adjustment. The question of competency to refuse medical treatment arose when he disallowed intervention for a suspected ear infection not confirmed by culture. Subsequently, the patient was alternately described as incompetent by a psychiatrist and competent by a medical ethics review panel. These decisions are interpreted within the context of existing medical-legal literature and historical precedent of competency in civil law. Central to competency evaluation is the patient's ability to recognize that a decision-making process is required, to review the pros and cons of various options, and to communicate a decision. Importantly, this decision need not be in accordance with the opinion of family or the health care team. Neuropsychological screening indicated the patient's cognitive abilities were within functional limits, and he subsequently agreed to treatment after experiencing pain and fever, and learning of a positive culture. It is concluded that a two-pronged neuropsychological evaluation of competency based on the patient's information processing capabilities is most appropriate in medical rehabilitation settings.